2001 Mazda MPV PO421 CODE

DEMETRISWILSON000

MEMBER
2001 MAZDA MPV

Engine Performance problem
2001 Mazda MPV 6 cyl 141000 miles

MY CAR TRIES TO START, THEN SHUTS OFF AFTER ABOUT 3 SECONDS, I KEEP TRYING TO START IT BUT IT JUST CRANKS AND NOT START. IT HAS HAPPENED BEFORE TWICE BUT IT STARTED AFTER SOME HOURS LATER. I TOOK IT TO CHECKERS FOR A DIAGNOSTIC AND GOT A CODE PO421, SO WHERE DO I GO FROM HERE, TO A ELECTRICAL SHOP OR REGULAR AUTO SHOP?

1 Reply

KHLOW2008

MECHANIC
41,815 POSTS

Hi demetriswilson000,

Thank you for the donation.

I have attached a brief explanation and testing procedures.

DTC P0421/P0431: WARM UP CATALYTIC CONVERTER EFFICIENCY BELOW LIMIT
Condition
DTC is set when PCM detects rear HO2S value difference becomes closer to value of front HO2S. PCM monitors when vehicle speed is 25-60 MPH, load is 22-45 percent and engine speed is 1000-3000 RPM.
Possible causes are:
� � � Warm Up Three Way Catalytic (WU-TWC) converter deterioration or malfunction.
� � � Exhaust system leaks.
� � � Loose front or rear HO2Ss.
� � � Front HO2S malfunction.

Guess you need to send it to the repair shop.